As a fixing device used for a copy machine or printer employing an electrophotographic system, a fixing device that performs heating and pressurization by using rollers is known. This fixing device includes a fixing roller that is heated to a high temperature, and a pressurizing roller that presses this fixing roller in contact with a recording sheet. In the fixing device, an unfixed image on the recording sheet is passed through a nip (operating part) formed by the fixing roller and the pressurizing roller, and the unfixed image on the recording sheet is thus fixed by heat and pressure.
In a color fixing device, unlike a monochrome fixing device, since four toner layers need to be fixed, smoothness of the toner surface after fixation is required in order to acquire high image quality. Therefore, a belt fixing device is often used. Also, recently, from the environmental view point (energy saving), a belt fixing device that uses an induction heating (IH) system of good thermal efficiency using a halogen lamp as a heat source is becoming employed.
However, though in the above example, a fixing belt as a heating unit on the image side is heated by an induction heating coil, an apparatus, particularly, a high-speed machine which is significantly deprived of heat has a disadvantage (problem) that it is difficult to simultaneously achieve high-speed heating, and maintenance of temperature and improvement in uneven gloss in continuous printing.